1. Field of the Invention
The present invention relates to a setting tool for driving-in fastening elements and, in particular, to a portable, internal combustion engine-driven setting tool including a guide tube for guiding a fastening element out of the tool and having a side cut-out through which a fastening element is displaced into the guide tube interior.
2. Description of the Prior Art
For pushing a fastening element out of a guide tube, a piston rod of a piston is driven into the guide tube for impacting the fastening element. A piston plate, which is secured on the piston rod is connected with a combustion chamber in which a driving power is generated upon ignition of a suitable combustible gas mixture, e.g., air/fuel gas mixture.
For safety reasons, in this type of setting tools often, there is provided a pressing sleeve displaceable over the guide tube. The pressing sleeve insures that the setting process, i.e., driving of a fastening element in an object can only then take place when the setting tool is pressed against the object. Upon the setting tool being pressed against an object, the pressing sleeve is displaced rearward with respect to the guide tube against a biasing force. The pressing sleeve, upon being displaced interact with mechanical and/or electrical switches which actuate an actuation element or trigger and/or provide for release of the drive energy only then when the pressing sleeve is depressed by a certain minimal amount.
The setting tools of this type are often equipped with magazines containing fastening elements and further include additional elements for determining, before initiating the setting process, if a magazine is mounted on the tool, if the number of fastening elements in the magazine is sufficient, if the fastening elements are correctly positioned in the magazine or the guide tube. Preferably, the fastening elements are arranged in strips in belt-like manner and in this condition are mounted in a tool magazine. The displacement of the magazine is effected under action of a biasing force for successively displacing the fastening elements in the interior of the guide tube so that they can be driven in an object.
An object of the present invention is to provide simple means for effecting one or several of the above-listed determining functions.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a feeler element extending into the interior of the guide tube opposite the side cut-out formed in the guide tube, with a depth by which the feeler element extends into the interior of the guide tube being determined by a fastening element to-be-displaced into the interior of the guide tube.
The depth, by which the feeler element extends into the interior of the guide tube permits to determine whether a fastening element has be displaced into the guide tube and whether, if displaced, is correctly positioned therein. If there is no fastening element in the guide tube or it has not been pushed into the guide tube out of the magazine sufficiently far, the feeler element would extend into the interior of the guide tube only so far that an initiation of the setting process and of the ignition of the combustible mixture in the combustion chamber would not be possible. In other words, the operation of the setting tool would be blocked until a fastening element is properly positioned in the guide tube in a position corresponding to a minimal depth by which the feeler element can extend into the interior of the guide tube.
According to one embodiment of this invention, the feeler element is formed as a section of a pawl pivotable in a plane containing the central axis of the guide tube, with pawl being pivotable about an axis extending transverse to the plane containing the central axis and having a locking edge which prevents displacement of a pressing sleeve displaceable over the guide tube in absence of a fastening element in the guide tube.
The feeler element according to the present invention provides simple means for blocking operation of the setting tool. If there is no fastening element in the setting tool or the fastening element is improperly positioned, the depth, by which the feeler element extends into the interior of the guide tube, exceeds a predetermined minimal depth. In this position of the feeler element, the locking edge lies in the displacement path of the pressing sleeve, preventing its displacement inside the tool when the tool is pressed against an object. The ignition of the combustible mixture is not possible until the pressing sleeve reaches its end position in which the ignition can take place.
Only when a fastening element is correctly positioned in the guide tube, the feeler element extends into the interior of the guide tube by a predetermined minimal depth and enables a rearward displacement of the pressing sleeve to its end position upon pressing the tool against an object so that ignition of the combustible mixture or firing of the tool becomes possible.
According to a further embodiment of the present invention, the pawl has an adjusting edge located between the locking edge and the feeler section and extending at an angle relative to the guide tube. The pressing sleeve is displaced along the adjusting edge for pivoting the feeler section out of the interior of the guide tube. Before the pressing sleeve reaches its rearward end position which provides for firing of the tool, the pawl is pivoted further away from the guide tube, and the feeler section is completely displaced out of the guide tube. As a result, a piston rod, displaceable, upon firing of the tool, into the guide tube, would not have any contact with the feeler section, whereby damage of the feeler section and/or the piston rod is prevented.
Preferably, the pawl is spring-biased in a direction toward the guide tube so that upon the fastening element leaving the guide tube and the piston rod moved to its initial position, the pawl is also pivoted into its initial position.
The novel feature of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both s to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.